F ire

DOE-HDBK-3010-94

1.0 Introduction

F ire: Generates heat and combustion gases that may destroy/stress the

radioactive material and/or the substrate upon which radioactive materials may

be deposited, compromise barriers, and/or pressurize containers/enclosure that

may lead to the airborne release of contained radioactive materials. Mass flux

of vapors from the reacting surfaces suspend material in air. This material is

then entrained in general convective currents that provide transport for

particulate materials.

E xp losion : Generates shock and blast effects with potential for gas flow

subsequent to the explosive event that may subdivide/deagglomerate and

entrain material. Explosive reactions may result from chemical (e.g.,

oxidations involving branch-chain products, oxidations of gas-oxidant

mixtures) or physical (overpressurization to failure of tanks or vessel, vapor

explosions) reactions. Shock waves are supersonic pressure waves (pulses)

that can transmit an impulse to materials and the surrounding structures

resulting in shattering of solid items. Shock waves are a true wave

phenomenon and involve little gross motion of propagating medium. The

potential for damage from shock waves has been extensively characterized.

Blast effects are typically subsonic and involve material entrained in the gas

flow. Blast effects are often more damaging. Blast effects are not subject to

the same reflection/amplification phenomena as shock waves because they have

significant momentum and inertia. The gas expanding from the explosion zone

carries material from the explosion site. If the explosion is adjacent to the

MARs, then blast effects can cause damage above and beyond the initial

impulse loading. Some explosive reactions may be followed by chemical

reactions, material vaporization, or fires that lead to substantial gas flows

following the explosive event. These gas flows may also entrain material.

Deflagrations do not involve shock, but can simulate blast effects. Under

proper conditions (e.g., confinement, structural features that enhance

turbulence), deflagrations can transition to detonations and produce shock

waves.

C riticality: Major hazard is unshielded radiation produced. Generates fission

products that may become airborne as well. Fission product gases are released

from liquid criticalities and from solid criticalities to the extent the underlying

critical mass is degraded. Solid fission products typically have small release

fractions determined by the degree of physical stress placed on the critical

mass itself. At large fission yields, solid critical masses may experience some

degree of melting or oxidation.

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